The present invention relates to a compressor bleed manifold having enhanced blade clearance control and particularly relates to a compressor bleed manifold mechanically isolated from the compressor casing load path.
The outer diameter compressor clearance is typically defined as the rotating blade to compressor casing inner wall radial distance. Generally, reducing the compressor clearance is desirable for improved performance. Current turbine single shell casing design requires the single shell to carry both the engine loads as well as to maintain a round, tight clearanced flow path. The problem of maintaining a tightly clearanced flow path is compounded by the typical compressor bleed air manifold which disrupts the smooth load path through the compressor casing, creates unsupported casing wall portions which lead to deflections radially inwardly or outwardly of the flow path, increases the flow path to bolted flange distance, limits extraction pipe locations and resultant loads onto the casing, and creates thermal response mismatches between the rotor and casing.
Compressor bleed manifolds conventionally include axially opposed cylindrical manifold sections having vertical flanges bolted to one another securing the axially opposite respective casing and manifold sections to one another. This vertical bolt circle lies a substantial distance radially outwardly from the flow path. The annular plenum of the manifold lies between the bolt circle through the vertical flanges and a continuous annular compressor bleed air slot opening radially between the flow path and the plenum. The wall portions defining the slot are typically unsupported and there is no continuous hoop load path through the casing portions adjacent the slot. Because the bolt circle is radially outwardly of the flow path, the stiffness and gravitational sag of the casing present problems with clearance control. Accordingly, there is a need for optimized clearance control at a compressor bleed air manifold.